1. Field of the Invention
The present invention relates to a color liquid crystal display (LCD) driver, and more particularly, to an improved color LCD driver with a YUV to RGB converter for converting data signals of a YUV type to data signals of a digital RGB type when an LCD controller transmits the data signals as the YUV type.
2. Discussion of the Related Art
The present invention relates to a number of methods for displaying a digital color image represented in a variety of methods, such as an RGB method for color computer graphics or a color TV, a YUV method for a broadcast system, a YIQ or YCrCb method, and a CMYK method for a color printer. The RGB method displays color using data signals of R (red), G(green), and B(blue). However, the YUV type displays color with a single Y signal (a luminance element), and U and V signals, which are chrominance elements.
As shown in FIG. 1, a conventional color LCD driver converts data signals of a digital RGB type outputted from an external LCD controller (not shown) into analog data signals, and then transmits the analog data signals to an LCD. The LCD driver comprises control logic 10 for outputting control signals which control input registers 20 in response to a control signal 20 received from the external LCD controller; the input registers 20 for sequentially storing the RGB data signals outputted from the external LCD controller according to the control signals outputted from the control logic 10; storage registers 30 for receiving and storing the RGB data signals stored in the input registers 20; a register string 40, wherein a plurality of resistances are connected serially, for selecting 64 points of the resistance having a desired voltage, thereby outputting voltage signals V0-V63 with 64 different levels in response to 9 voltage signals V0-V8 received from an external power supply; and a digital to analog converter (D/A converter) 50 for converting the digital RGB data signals stored in the storage registers 30 to analog data signals and then outputting the analog data signals to a column of an LCD panel (not shown) according to the 64 voltage signals outputted from the register string 40.
A data bus connected to an internal or external color LCD driver has a number of lines depending on the number of data bits corresponding to respective digital RGB data signals. That is, a data bus of 6 bits each for R (red), G (green), and B (blue), or 18 bits in total, is required to display 64 gray levels, and 8 bits each of R, G, and B, or 24 bits in total, are required to display 256 gray levels.
The operation of a conventional converter will now be described.
When the control signal and data signals of the RGB type received from the external LCD controller are inputted to the LCD driver, the control logic 10 outputs a control signal controlling the input registers 20 of the LCD driver. In response to the control signal outputted from the control logic 10, the input registers 20 sequentially store the digital RGB data signals received from the external LCD controller. After the digital RGB data signals are sequentially stored in the input registers 20, the storage registers 30 receive the digital RGB data signals and store them.
The register string 40, however, selects 64 points of a resistance producing desired voltage therein, thereby outputting voltage signals V0-V63 with 63 different levels in response to 9 voltage signals V0-V8 outputted from an external power supply.
Finally, the D/A converter 50 selects a voltage corresponding to the digital RGB data signals stored in the storage registers 30 by using the 64 voltage signals V0-V63 outputted from the register string 40, thereby converting the digital RGB data signals stored into analog data signals and outputting the analog data signals to the column of the LCD panel.
The conventional color LCD driver, however, must have a data bus corresponding to a number of the data signals of R (red), G (green), and B (blue). In other words, a data bus of 6 bits of R (red), G (green), and B (blue), or 18 bits total, is required to display 64 gray levels, and a data bus of 8 bits each of R, G, and B, or 24 bits total, is required to display 256 gray levels. Therefore, the pin count of an IC package connected to the data bus is so high that electric wiring becomes complicated, and a great deal of EMI (electromagnetic interference) is produced.